In view of the crucial role of human peroxisome proliferator-activated receptor gamma (PPARγ) in the development of several obesity-related cancers and as a potential therapeutic target for autoimmune and inflammatory diseases 15-17, we developed an improved Clover/mRuby2-based flow cytometry-based FRET assay which proved to be suitable for determination of both protein-protein interactions and alterations in protein binding intensity and affinity upon drug treatment of living cells. Here, PPARG is linked to obesity due to melanocortin 4 receptor deficiency.